MECHANISM OF STAEBLER-WRONSKI EFFECT - NEGATIVE EFFECTIVE-U AND POSITIVE EFFECTIVE-U NATURE OF THE BISTABLE DANGLING-BONDS IN A-SI, A-SI-H AND C-SI BY AB-INITIO MOLECULAR-DYNAMICS SIMULATION

The neutral (D-0) and charged (D-, D+) dangling-bonds are investigated by ab initio molecular dynamics simulation. The adiabatic potential s urfaces of dangling-bonds are calculated and two types of dangling-bon ds which show a negative effective-U for normal configuration and a po sitive effective-U for flipped configuration are found. Based on these results, a model for the mechanism of the Staebler-Wronski effect is proposed.